sguenther, glad you could easily figure it out. Everyone who has gotten this far should now know how to determine the size floaters need to be to join outer borders to the inner quilt center--not just for this quilt, but for all your quilts going forward. That is one of the beauties of a project like this--it teaches you a lot about the entire quiltmaking process.
If you want a detailed refresher on the process of figuring out what size to cut the "floater borders", I have a Tutorial on that here:
bbquiltmaker.blogspot.com/2016/04/tutorial-magic-of-floater-borders.html
For those who are eager for the cornerstone blocks--they are 6" finished stars. Sue's directions are for paper piecing and I'll write about that for the December 1 blog post. I did one that way and the rest with regular, standard piecing. The units in this 6" star are 2" units, Half Square and Quarter Square Triangles--very easy to figure out.